In the past, multi line telephone products with built-in intercoms have utilized separate sets of wire pairs to implement the telephone communications and the intercom communications, respectively. However, the use of a separate wire pair to implement the intercom communication connections is problematic. Most buildings and houses are equipped with in place wiring for telephone systems only. In order to implement a typical intercom system, the in place wiring of the buildings or houses must be modified. The cost and inconvenience of such modifications can be significant.
It would be advantageous to be able to implement an intercom channel or channels on the same wire pair used for telephone communications. Therefore, it is an object of the present invention to provide an intercom system in which the intercom communication channels are implemented on a local telephone network.
It is a further object of the present invention to provide an intercom system wherein voice signals are transferred between intercom units on a series of frequency modulated channels that are carried on a wire pair of a local telephone network.
It is another object of the present invention to provide an improved method and apparatus for controlling access to the intercom channel or channels.